Electric discharge device



May 26, 1936. w. J. SCOTT ELECTRIC DISCHARGE DEVICE- Filed Feb. 27', 1935 lNVENTOR Wil liam J. Scott ORNEY Patented May 26, 1936 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE DEVICE Application February 27, 1935, Serial No. 8,561 In Great Britain March 5, 1934 6 Claims.

This invention relates to the manufacture of electric discharge devices and more particularly to an improved method 01 making high pressure gaseous or vapour filled lamps.

' The object of this invention is to produce an improved lamp of the above type which will be simple to construct and which will be robust and inexpensive.

Lamps have hitherto been constructed in which a self-heating oxide coated electrode has been used, the electrode being supported on leading-in wires which pass through and are sealed into the glass envelope of the lamp but this sealing-in is a relatively expensive operation and there is difficulty in keeping the ends of the lamp sumciently hot during normal operation of the lamp.

According to the present invention I provide a lamp in which the discharge takes place in a high pressure of a mixture of mercury vapour and the vapour or gas of another suitable vaporizable material such as cadmium, the mercury being entirely vaporized but the other material being only partially vaporized. The cadmium or other material which is not evaporated or is condensed collects in cooled pockets at the ends of the lamp and acts as the lamp cathode. In order to ensure of the cadmium so acting an excess of it may be inserted in pockets formed by metal caps fused in the glass at each end of the lamp, the pockets being kept cool by suitable cooling means such as radiating fins. The anode function may be performed either by the metal cap itself or by a projection from it. In the preferred construction a glass and metal are used in the making of the lamp which have substantially the same co-efiicients of expansion up to the softening point of the glass to facilitate the joining of the parts. The accompanying drawing illustrates various methods of carrying this invention into effect.

In Fig. 1 the glass envelope I is provided with a metal end cap 2 having a pocket or recess 3 containing the cadmium or other material which is to be inserted in the lamp. The metal cap is fused'directly to the glass and the pockets may be kept cool by being provided with radiating fins, such as shown at 4. The anode function may be performed by the cap 2 or by projections from it such as shown at 5 in Fig. 2. In this form the cap 2 is dished so as to protect the seal between the metal and the glass from the heat of the discharge. In Fig. 3 I have shown a conical end cap 2 which is provided with an integral shield 6 which while protecting the seal from the heat of the discharge also prevents the glass from being blackened. The cap shown in Fig. 4 is similar to Fig. 1 but in this case an annular metal disc I is sealed into the glass a short distance in front of the cath- 5 ode. This disc acts to prevent sputtering of the cathode and blackening and also may operate as a starting electrode or grid for the discharge. In Fig. 5 the cathode is constructed in the form of a hollow cylinder and the envelope is drawn 10 down and sealed to its outer side. The inner end of the cylinder projects into the envelope and acts as an anode during the operation of the device. Fig. 6 shows a construction similar to that shown in Fig. 5 except that the cylinder is provided with a flange 8 to which the drawndown end of the envelope is sealed. The lamp may be provided with a vacuum jacket in which case a portion of the pockets may project through the wall of the jacket.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A gaseous electric discharge lamp comprising in combination a sealed envelope, a quantity of mercury and another vaporlzable material therein, the quantities of the vaporizable materialsbeing such that during operation of the lamp the mercury can be entirely vaporized and they other material only partially vaporized, means to supply sumcient electrical energy to the lamp to completely vaporize the mercury and a cathode for the lamp consisting of the unevaporated portion of said other vaporizable material.

2. A gaseous electric discharge lamp comprising in combination an envelope, a quantity of mercury and another vaporizable material therein, the quantities of the vaporizable materials being such that during operation of the lamp the mercury can be entirely vaporized and the other material only partially vaporized, means to supply sufficient electrical energy to the lamp to completely vaporize the mercury, caps sealed on the ends of the envelope and recesses in said caps containing the unevaporated portion of the other vaporizable material.

3. A gaseous electric discharge lamp comprising in combination an envelope, a quantity of mercury and another vaporizable material therein, the quantities of the materials being such that during operation of the lamp the mercury can be entirely vaporized and the other material only partially vaporized, means to supply suflicient electrical energy to the lamp to completely vaporize the mercury, caps sealed on the ends of the envelope, recesses in said caps containing the unevaporated portion of the other vaporizable material and heat radiating fins secured to the outer walls of said recesses.

4. A gaseous electric discharge lamp comprising in combination an envelope, a quantity of mercury and another vaporizable material therein, the quantities of the materials being such that during operation of the lamp the mercury can be entirely vaporized and the other material only partially vaporized, means to supply suiiicient electrical energy to the lamp to completely vaporize the mercury, caps sealed on the ends of the envelope, recesses in said caps containing the unevaporated portion of the other vaporizable material and portions projecting from the recesses into the interior of the lamp, said projections acting as anodes.

5. A gaseous electric discharge lamp comprising in combination an envelope, a quantity of mercury and another vaporizable material therein, the quantities of the materials being such that during operation of the lamp the mercury can be entirely vaporized and the other material only partially vaporized, means to supply sumcient electrical energy to the lamp to completely vaporize the mercury, a cathode for the lamp consisting of the unevaporated portion 01' the other vaporizable material, caps secured to the ends of the envelope and recesses in the caps in which the cathodes are situated.

6. A gaseous electric discharge lamp comprising in combination an envelope, a quantity of mercury and another vaporizable material therein, the quantities of the materials being such that during operation of the lamp the mercury can be entirely vaporized and the other material only partially vaporized, means to supply sumcient electrical energy to the lamp to completely 1 vaporize the mercury, a cathode for the lamp consisting of the unevaporated portion of the other vaporizable material, caps secured to the ends of the envelope, recesses in the caps in which the cathodes are situated and metal discs secured to the walls of the envelope in proximity to the cathodes.

WILLIAM JOSEPH SCO'I'I. 

